Hi all, This is my first time on this forum -- and I am *hoping* to be a Supra owner very soon (depending on answers to the below ha)...

Hoping for a little bit of help here. I test drove a 2005 21v today with the Indmar "assault" 325 5.7L, 230 hrs per the dash, no maintenance records to speak of. There was a knocking at idle and low RPMs, not sure that it completely went away at higher RPMs / under load, but it was definitely harder to hear (with the compartment closed it was completely undetectable -even hard to hear at idle - with it open it was still tough to hear if the knocking was even happening anything above ~2500 rpm). Based on some research it sounded almost like it could be a rod knocking, but I am a bit too novice to really be able to identify 100%, plus it didn't get louder or worse with high RPMs and the engine under load (including after filling the 1250lb ballast). I've asked the dealer for info/diagnostics on it, but since they're trying to sell me the boat I'm not certain I trust their diagnosis.

The dealer did say they inspected and compression tested the engine and everything checked out, though I have not personally seen the results. The knocking was relatively mild but definitely not something they would miss. On the test drive, the boat ran and performed beautifully other than the knock, even had a very smooth and normal idle (maybe 600-700rpm). It is also in phenomenal condition (garage kept practically show room condition boat), so I'm trying to determine if the knocking is a reason not to buy.

Couple of questions:
- Would the compression test detect something wrong with a rod?
- Could the compression testing detect any kind of OTHER (non rod) knocking problem?
- Are there other common piston-knocking sounds that are not as major as a rod issue?
- Would a rod knocking issue ever be an easy or cheap fix (from the research it sounds pretty major across the board)?
- Any idea on a ballpark repair cost if it IS a rod (considering its not something I am skilled enough to do myself)?

- What other questions should I be asking about this to probe the dealer and help figure out my level of risk?

Thanks for the help!